The subject invention may be utilized with various tufting systems, however, it has particular utility when used with one embodiment of the "Spanel tufting system" discussed hereinafter. In the "Spanel tufting system", the use of pneumatic transportation means for the yarn facilitates multicolor selection. In various embodiments of the Spanel techniques, yarn is severed prior to tufting and yarn clamps are necessary to either engage the yarn before it is severed or after it is severed during the actual tufting operation.
Basics of the "Spanel tufting system" are described in existing Spanel patents, including U.S. Pat. No. 3,554,147, which issued to Abram N. Spanel and George J. Brennan on Jan. 12, 1971 and U.S. Pat. No. Re 27,165 which issued Aug. 10, 1971 to Abram N. Spanel and Loy E. Barton.
The aforementioned U.S. Pat. No. Re. 27,165 discloses a pneumatic yarn transport system in which yarn is transported pneumatically to a tufting station where it is applied by tufting elements to a backing. Multi-color selection of the yarn bits is carried out by a magazine which provides yarns of various colors to each of guide tubes wherein the yarn is severed into bits to be transported to tufting elements.
The aforementioned U.S. Pat. No. 3,554,147 describes an alternative system to U.S. Pat. No. Re 27,165 and provides for the simultaneous selection of bit-lengths of yarn of various colors for each tufting cycle at each individual tufting station. A collator structure is utilized in which individual channels transport yarn into a common passageway adjacent the tufting station. In a preferred embodiment, severing takes place in close proximity to the tufting station after a selected yarn strand has been fed into the common passageway.
In U.S. Pat. No. 3,937,159, which issued to Abram N. Spanel on Feb. 10, 1976, various yarn clamping means for tufting apparatus are disclosed. These clamps have utility with either the Spanel (Barton) system of U.S. Pat. No. Re 27,165 or the Spanel (Brennan) system of U.S. Pat. No. 3,554,147.
Yarn clamp structure is also shown in FIGS. 11 and 12 of U.S. Pat. No. 3,670,672, which issued to Abram N. Spanel and John L. Schwartz on June 20, 1972.
In tufting developments which utilize the Spanel concepts, Ellison British Specification No. 1,339,594 discloses a clamp means which may also be used with Spanel-type tufting apparatus.
In a preferred mode of operation of Spanel tufting, as disclosed in co-pending Patent application Ser. No. 811,955, filed concurrently herewith, a yarn adjuster enables a Spanel tufting machine to operate with a tuft length selectivity feature. To improve the operation of the yarn adjuster, it is necessary to prevent the impalement of yarn by the tufting needles which without preventive measures can occur because of the close proximity of the yarn adjuster to the tufting needles.